Molecular fingerprints in the blink of a laser

The technique, called field-resolved spectroscopy (FRS), was developed by an international team, including researchers affiliated with King Saud University in Saudi Arabia. The approach illuminates a biological sample with powerful, ultra-short pulses from infrared lasers, causing it to emit an electrical field that is then measured using a method called electro-optic sampling. FRS isolates the signal generated by molecules within the sample from background excitation, which is orders of magnitude stronger. This improved ‘signal-to-noise ratio’ means weaker molecular signals can be detected compared to existing approaches. The technique’s sensitivity, coupled with the ability to use a stronger power source, also makes it possible to use thicker biological samples.

The team found that FRS out-performed existing methods in measuring blood serum samples spiked with a chemical, and in measuring small changes in the relative concentration of two different sugar molecules in solution. They also showed FRS could fingerprint molecular ensembles in human cell cultures and intact plant leaves. 

“It’s very hard to foresee all the possible applications,” says physicist, Ioachim Pupeza, of the Max Planck Institute of Quantum Optics, in Germany, who was among its developers. Pupeza says that the improved sensitivity could offer benefits to basic research in diverse fields, as well as in medical diagnostics.

For now, FRS is only a prototype. The researchers are working to develop the next generation of the device, which will offer broader spectral coverage and higher sensitivity, as well as better engineering than the prototype. “We expect that deployment of the technology to other labs and clinics will be possible soon,” says Pupeza.

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